The present invention relates to vitreous silica-based plastic refractory mixes and plastic refractories bonded with aluminum phosphate which have a long shelf life, low bulk densities as compared to other plastics, excellent resistance to both acids and alkalies, high-strengths, excellent thermal shock resistance and good abrasion resistance.
Plastic refractories are well known products, namely being mixtures of ground refractory materials in stiff plastic form suitable for ramming into place to form monolithic linings. These plastic refractories are commonly installed by hand using mallets or by conventional pneumatic hammers. Such plastics are utilized in making rapid repairs in a wide variety of vessels as well as for forming monolithic linings for heating furnaces, boiler settings, forging ovens, annealing ovens and furnaces, cupolas, magnesium electrolytic cells, titanium chlorinators, in certain areas of incinerators, in devices used to refine petroleum, and many other industrial applications where the lining is prone to thermal shock and acid or alkali contact at high temperatures.
A number of different refractories have been utilized in order to make a plastic which will be resistant to both acid and alkalies, have better creep resistance at high temperatures and thermal shock resistance as well as a suitable shell life. It has been known to primarily use aluminous or silicon carbide aggregates as well as various types of bonding phases, primarily aluminum phosphate in order to increase the strength, acid resistance and thermal shock resistance, but such plastics still have been unsatisfactory.
Salazar U.S. Pat. No. 4,440,865 discusses a means of improving the shelf life and wet strength of plastics. This patent describes use of perlite, which is a form of silica, but it is weak and friable and could not be used in a plastic which is rammed during installation.